Kraly F S, Cushin B J, Smith G P
J Comp Physiol Psychol. 1980 Apr;94(2):375-87. doi: 10.1037/h0077663.
Rats eat more at night than during the day. This work investigated whether this nocturnal hyperphagia is characterized by increased hunger, decreased postprandial satiety, or both. Rats were presented with liquid food after 3-hr food deprivation at the midpoint of the night or day phase of a 12:12 hr light/dark cycle. Quinine adulteration of food produced equal percentage suppression of first meal size (MS) and of 60-min intakes in the night and the day. This suggests that rats are equally hungry after 3-hr food deprivation in the night and the day. In contrast to apparently equal hunger, rats were less satiated by ingested food after 3 hr of food deprivation at night than during the day. This conclusion is based on the observations that the postprandial intermeal interval (IMI) was significantly shorter at night and that the satiety ratio (IMI/MS) was smaller at night. This nocturnal decrease in the satiating potency of ingested food was demonstrated for two specific preabsorptive satiety mechanisms: (a) the pregastric satiety mechanism(s) stimulated by sham feeding and (b) cholecystokinin, the putative satiety hormone released by food contacting the mucosal surface of the upper small intestine. All the results suggest that the diurnal variation of food intake in rats is primarily the result of diurnal variation in the potency of postprandial satiety mechanisms.
大鼠夜间进食比白天多。这项研究调查了这种夜间多食是由饥饿感增加、餐后饱腹感降低还是两者共同导致的。在12小时光照/12小时黑暗周期的夜间或白天阶段的中点，对大鼠禁食3小时后给予液体食物。食物中添加奎宁对夜间和白天第一餐食量（MS）以及60分钟摄入量的抑制百分比相同。这表明大鼠在夜间和白天禁食3小时后饥饿程度相同。与明显相同的饥饿感形成对比的是，夜间禁食3小时后，大鼠摄入食物后的饱腹感低于白天。这一结论基于以下观察结果：夜间餐后餐间间隔（IMI）明显更短，且夜间饱腹感比率（IMI/MS）更小。对于两种特定的吸收前饱腹感机制，即（a）假饲刺激的胃前饱腹感机制和（b）胆囊收缩素（一种由食物接触上段小肠黏膜表面释放的假定饱腹感激素），均证明了夜间摄入食物的饱腹感效力降低。所有结果表明，大鼠食物摄入量的昼夜变化主要是餐后饱腹感机制效力昼夜变化的结果。
